They Try , I got flashed last year in the UK with my Mrs motor ( German Reg) they get all the details from the German DVLA and give them over to a Firma called CP who issue the fine with hefty costs for there troubles 
after about 6 reminders and more costs they sell the dept to a German Soliciter who also send a few letters.By german law they have got to prove who was driving and my wife is not obliged by law to name me as the driver so it ends up in the bin.